Проверка на пустоту.

unit Unit1;
 
interface
 
uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  Grids, StdCtrls, Menus;
 
type
  TForm1 = class(TForm)
    StringGrid1: TStringGrid;
    MainMenu1: TMainMenu;
    N1: TMenuItem;
    N4: TMenuItem;
    Kurs1: TMenuItem;
    N3: TMenuItem;
    N2: TMenuItem;
    Label1: TLabel;
    Edit1: TEdit;
    CheckBox1: TCheckBox;
    procedure FormCreate(Sender: TObject);
    procedure N4Click(Sender: TObject);
    procedure Kurs1Click(Sender: TObject);
    procedure N3Click(Sender: TObject);
    procedure N2Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;
 
var
  Form1: TForm1;
  f:Text;
 
implementation
 
uses Unit2, Unit5, Unit4;
 
 
 
{$R *.DFM}
 
 
procedure TForm1.FormCreate(Sender: TObject);
begin
 Form1.StringGrid1.Cells[0,1]:='Доллары';
  Form1.StringGrid1.Cells[0,2]:='Фунт';
  Form1.StringGrid1.Cells[0,3]:='Марка';
  Form1.StringGrid1.Cells[0,4]:='Евро';
 
  Form1.StringGrid1.Cells[0,0]:='Название';
  Form1.StringGrid1.Cells[1,0]:='Курс';
  Form1.StringGrid1.Cells[2,0]:='Пересчет';
 
 end;
 
 
procedure TForm1.N4Click(Sender: TObject);
begin
  Form1.Close;
end;
 
procedure TForm1.Kurs1Click(Sender: TObject);
  var
  min,max,i:integer;
  mins,maxs:string;
  j: integer;
  flag: boolean;
 
begin
flag:=false;
if Form1.StringGrid1.Cells[1,j] = '' then ShowMessage ('Vvedite znachenie');
begin
flag:=true;
if Form1.StringGrid1.Cells[1,j] <> '1..0' then
  mins:=Form1.StringGrid1.Cells[0,1];
  min:=StrToInt(Form1.StringGrid1.Cells[1,1]);
  for i:=2 to 4 do
    if StrToInt(Form1.StringGrid1.Cells[1,i])<min then
      Begin
        min:=StrToInt(Form1.StringGrid1.Cells[1,i]);
        mins:=Form1.StringGrid1.Cells[0,i];
      End;
  maxs:=Form1.StringGrid1.Cells[0,1];
  max:=StrToInt(Form1.StringGrid1.Cells[1,1]);
  for i:=2 to 4 do
    if StrToInt(Form1.StringGrid1.Cells[1,i])>max then
      Begin
        max:=StrToInt(Form1.StringGrid1.Cells[1,i]);
        maxs:=Form1.StringGrid1.Cells[0,i];
        End;
         Application.CreateForm(TDialog1, Dialog1);
         Dialog1.Label2.Caption:=mins;
        Dialog1.Label4.Caption:=maxs;
end;
end;
 
 
 
 procedure TForm1.N3Click(Sender: TObject);
begin
  Application.CreateForm(TDilaog3, Dilaog3);
 
end;
 
 
procedure TForm1.N2Click(Sender: TObject);
 Var
  i:integer;
begin
 if Edit1.Text='' then ShowMessage('Введите сумму')
 else for i:=1 to 4 do
 begin
  if StringGrid1.Cells[1,i]<>'' then
  if CheckBox1.Checked then
  StringGrid1.Cells[2,i]:=FloatToStrF(kurs(StrToFloat(Edit1.Text),StrToFloat(StringGrid1.Cells[1,i])) ,   ffFixed,10,2)
else
StringGrid1.Cells[2,i]:=FloatToStr(kurs(StrToFloat(Edit1.Text),StrToFloat(StringGrid1.Cells[1,i])));
end;
end;
 
end.